1. Technical Field
The embodiments herein generally relate to wireless communication, and, more particularly, to a method and an apparatus for timing and frequency acquisition in a MediaFLO™ (Forward Link Only) mobile multimedia multicast system.
2. Description of the Related Art
In recent years, the wireless industry has seen explosive growth in device capability, especially in relation to mobile devices, such as cell phones, handhelds, gaming consoles, etc. Ever-increasing demand for computing power, memory, and high-end graphic functionalities has accelerated the development of new and exciting wireless services. In the last few years, multiple technologies have been proposed to address delivery of streaming multimedia to mobile devices.
Multimedia communications provide a rich and immediate environment of image, graphics, sound, text and interaction through a range of technologies. An example of multimedia communication is streaming multimedia, which is primarily a delivery of continuous synchronized media data. The streaming multimedia is constantly received by, and displayed to an end user while it is being delivered by a provider. Multiple technologies such as Integrated Services Digital Broadcasting-Terrestrial (ISDB-T), Terrestrial-Digital Multimedia Broadcasting (T-DMB), Satellite-Digital Multimedia Broadcasting (S-DMB), Digital Video Broadcasting-Handheld (DVB-H), and FLO (Forward Link Only) are used to address the delivery of streaming multimedia to mobile devices. These technologies have typically leveraged upon either third generation cellular/PCS, or digital terrestrial TV broadcast technologies.
For delivering unprecedented volumes of high-quality, streaming or clipped, audio and video multimedia to wireless subscribers, an air interface has been developed based on FLO technology for MediaFLO™ mobile multimedia multicast system available from Qualcomm, Inc., Calif., USA. MediaFLO™ or media forward link only is a combination of the media distribution system and the FLO technology. The FLO technology is the ability to deliver a rich variety of content choice to consumers while efficiently utilizing spectrum as well as effectively managing capital and operating expenses for service providers. The details of the MediaFLO mobile multimedia multicast system are available in Chari, M. et al., “FLO Physical Layer: An Overview,” IEEE Transactions on Broadcasting, Vol. 53, No. 1, March 2007, the contents of which, in its entirety, is herein incorporated by reference.
FLO technology was designed specifically for the efficient and economical distribution of the same multimedia content to millions of wireless subscribers simultaneously. Also, the FLO technology was designed from the ground up to be a multicasting network, which is overlaid upon a cellular network. It does not need to support any backward compatibility constraints. Thus, both the network infrastructure and the receiver devices are separate from those for the cellular/PCS network. Moreover, as the name suggests, the technology relies on the use of a forward link (network to device) only.
FLO enables reducing the cost of delivering such content and enhancing the user experience, allowing consumers to “surf” channels of content on the same mobile handsets they use for traditional cellular voice and data services.
MediaFLO™ technology can provide robust mobile performance and high capacity without compromising power consumption. The technology also reduces the network cost of delivering multimedia content by dramatically decreasing the number of transmitters needed to be deployed. In addition, MediaFLO™ technology-based multimedia multicasting complements wireless operators' cellular network data and voice services, delivering content to the same cellular handsets used on 3G networks.
The MediaFLO™ wireless system has been designed to broadcast real time audio and video signals, apart from non-real time services to mobile users. The system complements existing networks and radically expands the ability to deliver desired content without impacting the voice and data services. Operators can leverage the MediaFLO™ system to increase average revenue per user (ARPU) and reduce churn by offering enhanced multimedia services. Content providers can take advantage of a new distribution channel to extend their brand to mobile users. Device manufacturers will benefit from increased demand for multimedia-enabled handsets as consumer appetite grows for the rich content provided through MediaFLO™ systems.
The MediaFLO™ service is designed to provide the user with a viewing experience similar to a television viewing experience by providing a familiar type of program-guide user interface. Users can simply select a presentation package, or grouping of programs, just as they would select a channel to subscribe to on television. Once the programs are selected and subscribed to, the user can view the available programming content at any time. In addition to viewing high quality video and audio content and IP data, the user may also have access to related interactive services, including the option to purchase a music album, ring tone, or download of a song featured in a music program. The user can also purchase access to on-demand video programming, above and beyond the content featured on the program guide.
The respective MediaFLO™ system transmission is carried out using tall and high power transmitters to ensure wide coverage in a given geographical area. Further, it is common to deploy 3-4 transmitters in most markets to ensure that the MediaFLO™ system signal reaches a significant portion of the population in a given market. During the acquisition process of a MediaFLO™ system data packet several determinations and computations are made to determine such aspects as frequency offsets for the respective wireless receiver. Given the nature of MediaFLO™ system broadcasts that support multimedia data acquisitions, efficient processing of such data and associated overhead information is paramount. For instance, when determining frequency offsets or other parameters, complex processing and determinations are required where determinations of phase and associated angles are employed to facilitate the MediaFLO™ system transmission and reception of data.
The FLO system is comprised of two parts: (a) The FLO network, which includes the collection of transmitters and the backhaul network, and (b) The FLO device, which may be any type of communicating devices such as a cell phone, computer, personal assistant, laptop, handheld, or gaming consoles, etc. FIG. 1 illustrates a FLO system 100 for a MediaFLO™ system. The system 100 includes one or more transmitters 110 that communicate across a wireless network 130 to one or more receivers 120.
The FLO system 100 is utilized in developing an air interface for the MediaFLO™ mobile multicast system. The air interface uses Orthogonal Frequency Division Multiplexing (OFDM) as the modulation technique, which is also utilized by Digital Audio Broadcasting (DAB), (DVD-T), and (ISDB-T).
To ensure that the user experience is as uniform as possible over the entire coverage area and optimize spectral efficiency and network economics, FLO system 100 employs the concept of Single Frequency Network (SFN) operation.
Typically, the address generation logic accepts an input address data ranging between 0 and 1023 and generates an output address data lying between 0 and 1023. However, an address generation logic utilized in a turbo decoder also accepts tail bits addresses along with the input address data. Furthermore, an output address data having a value more than 993 is considered invalid and accordingly discarded.
FIG. 2 illustrates a conventional address generation module 200 according to the MediaFLO™ specification, adapted to translate the address of information as explained in conjunction with FIG. 1. The address generation module 200 comprises a small look-up table (LUT) 202 and a multiplier 204. The LUT 202 and the multiplier 204 are adapted to work with other associated circuitry, such as an adder module 206, a bit-reversing module 208 and an output module 210, for translating the address of information. Further, the address generation module 200 is provided with a 10 bit input address data 212, which is processed to generate an output address data 214. As explained earlier, the output address data 214 may have a value ranging between 0 and 1023. However, the output address data 214 must have a value less than or equal to 993 to be considered valid by the address generation module 200. The output module 210 of the address generation module 200 is adapted to determine the validity of the output address data 214 by determining a value of the output address data 214.
However, a conventional address generation module, such as the address generation module 200, does not guarantee a valid output address data 214 each time the input address data 212 is processed. Upon encountering the invalid output address data 214 for a particular input address data 212, the address generation module 200 discards the output address data 214. Thereafter, the address generation module 200 increments the input address data 212 by 1 and processes the new input address data to generate a corresponding output address data. Further, the new output address data is analyzed by the output module 210 for determining validity of the output address data. Accordingly, generation of a valid output address data 214 by the address generation module 200 may be a lengthy process. More specifically, the address generation module 200 may, in certain cases, require two clock pulses to generate a valid output address data 214.
Further, the address generation module 200 only accepts sequential input, which has a starting value of 0. However, a sliding window turbo decoder, which is a widely used in a Very Large Scale Integration (VLSI) implementation of the turbo decoder, does not accept a sequential input. Also, an input address data to the sliding window turbo decoder does not have a starting value of 0. Accordingly, the address generation module 200 cannot be utilized in the sliding window turbo decoders.
A known approach to meet the above problems is to implement a large LUT in the address generation module 200. The large LUT may have 994 possible entries of valid output address data and corresponding input address data. Each entry of the LUT is of 10 bits. However, implementation of the large LUT in an application specific integrated chip (ASIC) chip may utilize a large area of the ASIC chip. Alternatively, the large LUT may require a standalone read only memory (ROM) to store the 994 entries. Further, to achieve a high data rate with a low clock rate, the Turbo decoder may utilize multiple sliding windows, thereby requiring multiple ROMs for each of the sliding windows. Implementation of multiple ROMs in the ASIC chip may occupy a substantial area of the chip, which is undesirable.
Accordingly, there persists a need for an address generation module, which is adapted to meet the afore-mentioned shortcomings of the conventional solutions. More specifically, there persists a need for an address generation module, which generates a valid output address data with out requiring a large memory space. Moreover, there persists a need for an address generation module, which generates a valid output address data with lesser number of clock pulses as compared to the conventional solutions.